Experimental Study Of Flat Heat Pipes With Non-uniformed Grooved Geometries

With the rapid development of electronic information technology,high frequency and miniaturization trend of electronic component puts forward a higher requirements on thermal management technology.As a high-efficiency element for heat transfer,heat pipe is considered to be a promising potential technology in the heat management industry,for its simple structure,low cost,high thermal conductivity and environment adaptability.How to minimize the thermal resistance and increase the critical heat flux has been the main trend as research continues.Two kinds of flat heat pipes with non-uniform grooved geometries were fabricated in this paper.Based on the experimental system,the startup and heat transfer performance were studied.The main contents and conclusions are as follows:(1)The response characteristics of pressure and temperature were monitored by time.When the heat pipe starts,the pressure suddenly rises and fluctuates.In this paper,the thermal resistance R is taken as a key parameter to evaluate the phase change heat transfer performance of the heat pipes.The difference of heating power brings different response status of R.In general,at a lower power(60w),the working fluid does not boil.Heat transfers through internal thermal conductivity and surface evaporation of the fluid.The thermal resistance reaches a stable state after rising;In the power range from 100 W to 150 W,phase transformation takes place until being heated several minutes.The thermal resistance R declines first,and then tend to be stable;When the heating power goes too high(210W),the thermal resistance rebounds after a little decrease.The higher heating power,the greater thermal resistance gets after rebounding.(2)The variation of startup performance,thermal resistance and heat source temperature with heating power was studied in 60W~360W.The results show that the startup time decreases with heating power for the heat pipes.And the crossed grooved flat heat pipe has a better startup performance under the same charge ratio.In I60 W ~ 170 W the heat transfer performance of the herring grooved flat heat pipe is better.While the crossed grooved flat heat pipe gets a lower heat source temperature and a better anti-dry performance,moreover,its temperature of bottom plate is more uniform.(3)The heat transfer performance was studied at 0%~90% charge ratio with deionized water working as medium fluid.It is found that: At the same heating power,the higher the charge ratio is,the longer startup time needed for the heat pipes.The variation of thermal resistance with charge ratio presents two trends when the given heating power is different.With the increasing of charge ratio,the thermal resistance decreases firstly,and then increases when the heating power is less than 150 W.However,it drops rapidly and then keeps stable when the power is more than 150 W.